follow path constraint lost
The question, what is the result of first converting  a Bezier curve to a mesh and then back to a curve is still interesting. But I found a way to solve my original problem. I think it is not a work-around but the proper way of doing it. I needed to extend a Bezier curve by a new curve of fixed precomputed length. This is what I do: I generate an auxiliary  polygon of the desired length exactly in the place where I need the extended curve with the help of &quot;measurelt&quot;.  Then I extend the Bezier curve following the polygon. Then I delete the auxiliary polygon.